This paper reviews the method for making absolute ultrasonic attenuation measurements by means of nondestructive testing transducers and liquid buffer columns or solid buffer rods. The principle is that the transducer must be separated from the specimen so that the transducer cannot influence the echoes in the specimen. Then the attenuation coefficient in the specimen and the reflection coefficient at the buffer/specimen interface can be calculated from the amplitudes of the first three echoes in the buffer/specimen system. For absolute measurements, the amplitudes must be corrected for ultrasonic beam spreading (diffraction). The theory of the measurements and the corrections is recapitulated, and experimental examples are given showing the utility of the method. Experimental techniques are also recapitulated.